Personal computer diskettes and similar memories may contain an operating system or may contain only data. Many operating systems are outstanding and will be developed in the future. The loading of an operating system to control the computer (commonly termed booting or to boot) typically includes reading the diskette to establish that the diskette is not a formatted diskette, which carries a single code repetitively. If that test is satisfied, the typical system passes booting control to the code on the diskette. When that code proves not to constitute an operating system, the computer will signal an error and wait for operator intervention. The signal typically is a message telling the operator to insert a system diskette and once again initiate booting. Thus, an error message and operator action are inevitable unless the operator has inserted a diskette having a valid operating system.
The majority of operating systems employ a similar convention for placing the operating system on the diskette and for including code defining the information on the diskette. Different versions of various operating systems do implement the conventions slightly differently as to where key information is located on the diskette. This invention employs such conventions to determine with high probability of accuracy whether a diskette contains an operating system, permitting automatic booting of an alternate operating system and therefore minimal delay and operator inconvenience. Since normally a diskette left in the computer drive by mistake will be a data diskette, rather than a system diskette, automatically attempting to boot on code in an alternative memory often is consistent with the original intent of the operator.
As illustrated in FIG. 3, it is conventional for personal computers to boot from the code in alternative memory locations when no diskette or a formatted diskette is found in the original code examined for booting. Ultimately, these conventional systems execute Basic, a well-known operating system, from code stored in the permanent memory (termed read only memory or ROM) of the personal computer.